1. Field of the Invention
The present invention relates to an inferior-and-superior-limb blood-pressure index measuring apparatus which measures an inferior-and-superior-limb blood-pressure index of a living subject, and particularly to such an inferior-and-superior-limb blood-pressure index measuring apparatus which assures that angiopathy of a living subject can be diagnosed with high reliability.
2. Related Art Statement
There has been proposed an inferior-and-superior-limb blood-pressure index measuring apparatus which measures an inferior-and-superior-limb blood-pressure index of a living subject, that is, measures respective blood-pressure values of inferior and superior limbs of the subject and calculates, as the index, a ratio of one of the two blood-pressure values to the other. An example of this apparatus is disclosed in Japanese Patent No. 3,027,750 or its corresponding U.S. Pat. No. 6,379,309. The inferior-and-superior-limb blood-pressure index is used to evaluate a degree of arteriostenosis of an inferior limb that is caused by atheromatosis of a considerably large artery (i.e., atherosclerosis). Since a patient who feels numbness in his inferior limb is suspected to have arteriostenosis in the inferior limb, an inferior-and-superior-limb blood-pressure index is measured to make a diagnosis about the stenosis.
However, a diabetic patient may feel numbness that is caused by diabetic neuropathy derived from diabetic microangiopathy. Therefore, it has been difficult to make a reliable diagnosis on the cause of the numbness felt by the patient, based on the inferior-and-superior-limb blood-pressure index only.
It is therefore an object of the present invention to provide an inferior-and-superior-limb blood-pressure index measuring apparatus which assures that angiopathy of an inferior limb of a living subject can be diagnosed with high reliability.
The above object has been achieved by the present invention. According to the present invention, there is provided an apparatus for measuring an inferior-and-superior-limb blood-pressure index of a living subject, comprising an inferior-limb blood-pressure measuring device which measures an inferior-limb blood pressure of an inferior limb of the subject; a superior-limb blood-pressure measuring device which measures a superior-limb blood pressure of a superior limb of the subject; an inferior-and-superior-limb blood-pressure index determining means for determining the inferior-and-superior-limb blood-pressure index based on the inferior-limb blood pressure measured by the inferior-limb blood-pressure measuring device and the superior-limb blood pressure measured by the superior-limb blood-pressure measuring device; a heartbeat-synchronous-signal detecting device which detects a heartbeat-synchronous signal that is produced from the subject; a pulse-period-related-information obtaining means for obtaining, based on the heartbeat-synchronous signal detected by the heartbeat-synchronous-signal detecting device, pulse-period-related information that is related to a pulse period of the subject; and a neuropathy-related-information obtaining means for obtaining, based on the pulse-period-related information obtained by the pulse-period-related-information obtaining means, neuropathy-related information that is related to diabetic neuropathy.
According to the present invention, the inferior-and-superior-limb blood-pressure index determining means determines the inferior-and-superior-limb blood-pressure index, and additionally the neuropathy-related-information obtaining means obtains the neuropathy-related information that changes in relation with diabetic microangiopathy. Based on the inferior-and-superior-limb blood-pressure index and the neuropathy-related information, a medical person can make a reliable diagnosis on the angiopathy of the inferior limb of the subject.
According to a preferred feature of the present invention, the inferior-and-superior-limb blood-pressure index measuring apparatus further comprises a blood-pressure-measurement starting means for operating the inferior-limb blood-pressure measuring device and the superior-limb blood-pressure measuring device to start respective blood-pressure measuring operations, after a pre-set resting time has elapsed, and the pulse-period-related-information obtaining means obtains the pulse-period-related information based on the heartbeat-synchronous signal detected by the heartbeat-synchronous-signal detecting device during the resting time.
In order to measure a reliable inferior-and-superior-limb blood-pressure index, it is needed to measure inferior-limb and superior-limb blood-pressure values from the subject who is relaxed after having rested for a certain time. According to this feature, the blood-pressure-measurement starting means operates the inferior-limb blood-pressure measuring device and the superior-limb blood-pressure measuring device to start the respective blood-pressure measuring operations, after the pre-set resting time has elapsed. Thus, a reliable inferior-and-superior-limb blood-pressure index can be obtained. In addition, since the pulse-period-related-information obtaining means obtains the pulse-period-related information based on the heartbeat-synchronous signal detected by the heartbeat-synchronous-signal detecting device during the resting time, only a short time is needed to obtain both the inferior-and-superior-limb blood-pressure index and the neuropathy-related information.
According to another feature of the present invention, the inferior-and-superior-limb blood-pressure index measuring apparatus further comprises a neuropathy judging means for judging that the subject has the diabetic neuropathy, when the neuropathy-related information does not fall within a pre-determined normal range.
According to this feature, the neuropathy judging means automatically judges whether the subject has diabetic neuropathy.
According to another feature of the present invention, the neuropathy-related-information obtaining means determines, as the neuropathy-related information, a coefficient of variance of the pulse-period-related information, and the inferior-and-superior-limb blood-pressure index measuring apparatus further comprises an age input device for inputting an age of the subject; and a normal-range determining means for determining the normal range, based on the age inputted through the age input device, according to a relationship between age and lower limit of normal range wherein, as age increases, lower limit decreases.
According to this feature, the normal-range determining means determines, based on the age of the subject, the normal range that is to used by the neuropathy judging means. Therefore, the neuropathy judging means can make an accurate judgment about diabetic microangiopathy of each subject, older or younger.
According to another feature of the present invention, the inferior-and-superior-limb blood-pressure index measuring apparatus further comprises a display device which simultaneously displays the inferior-and-superior-limb blood-pressure index and the neuropathy-related information.
According to this feature, based on what is displayed by the display device, a medical person can easily judge whether the cause of numbness felt by of the subject is arteriostenosis of the inferior limb, or diabetic microangiopathy.
According to another feature of the present invention, the superior-limb blood-pressure measuring device comprises an upper-arm cuff that is adapted to be wound around an upper arm of the subject, and determines the superior-limb blood pressure based on a change of respective amplitudes of respective heartbeat-synchronous pulses of a cuff pulse wave that is produced in the upper-arm cuff while a pressure of the cuff is changed.
According to another feature of the present invention, the heartbeat-synchronous-signal detecting device detects, as the heartbeat-synchronous signal, the cuff pulse wave that is produced in the upper-arm cuff in a state in which the pressure of the cuff is maintained at a pre-set pressure that would be lower than a diastolic blood pressure of the subject.
According to this feature, it is not needed to employ a device which is worn on the subject for the exclusive purpose of detecting the heartbeat-synchronous signal.
According to another feature of the present invention, the inferior-limb blood-pressure measuring device comprises an inferior-limb cuff that is adapted to be wound around a portion of the inferior limb of the subject, and determines the inferior-limb blood pressure based on a change of respective amplitudes of respective heartbeat-synchronous pulses of a cuff pulse wave that is produced in the inferior-limb cuff while a pressure of the cuff is changed.
According to another feature of the present invention, the heartbeat-synchronous-signal detecting device detects, as the heartbeat-synchronous signal, the cuff pulse wave that is produced in the inferior-limb cuff in a state in which the pressure of the cuff is maintained at a pre-set pressure that would be lower than a diastolic blood pressure of the subject.
According to this feature, it is not needed to employ a device which is worn on the subject for the exclusive purpose of detecting the heartbeat-synchronous signal.